Communications and data transmission systems which transmit information signals in the form of optical pulses over a dielectric waveguide such as an optical fibre are now commonplace. Whilst improvements in the sources of the optical pulses and in the optical fibre waveguides have increased the range over which such signals can be transmitted to between 100 and 200 kilometers it is still necessary to regenerate the signals when they are transmitted over greater distances and when their power is reduced by beam splitting or being switched or otherwise handled. In a conventional regenerator, the optical signal is received by a photodiode and converted to an electrical signal. This electrical signal is then amplified and reshaped in an electronic regenerator circuit before being converted by an optical source into an optical pulse once again for onward transmission along the next optical fibre transmission line.